One of the most popular accessories for trucks and recreational vehicles is a truck box used to store and secure a variety of tools and other items. There are a number of different types of truck boxes, including cross-over boxes, side mount boxes, chest boxes, top mount boxes, RV boxes and others. Truck boxes of this type are typically formed of aluminum tread plate, and comprise a front wall, a back wall, a bottom wall and opposed end walls which are interconnected to form a hollow interior. The truck box interior is closed by a top wall or lid pivotal between open and closed positions on a hinge mounted to the back wall, usually with the assistance of gas springs.
Many of the truck boxes noted above have a lid with a substantial length or longitudinal dimension as measured between the end walls of the box compared to its width, e.g. the distance between the front and back walls. Cross-over boxes, for example, span the entire width of a truck bed from one side wall to the opposite side wall. Users wishing to access the interior of the cross-over box typically stand to one side of the truck bed, along one of the vehicle side walls, and grasp the lid near one end to open or close it. Repetitive motions of opening and closing the lid, particularly when it is grasped from one side or the other, have a tendency to twist, torque and/or bend the lid which can lead to misalignment with the remainder of the truck box when the lid is closed.
One approach to addressing this problem which is found in the prior art involves providing a cavity in the truck box lid which is formed between a top sheet and a liner sheet connected to one another by welding or similar means. An expansible, self-curing foam is injected into the cavity, which, when cured, fills the entirety of the cavity and adheres to both the top sheet and the liner sheet. See, for example, U.S. Pat. Nos. 7,168,590; RE42,964; and 6,830,167. Tonneau covers for the beds of trucks have also employed this construction, either using expansible, self-curing foam injected into a cavity of the cover, or, previously cured foam which is cut from a sheet and adhered in place. See, for example, U.S. Pat. Nos. 6,431,633 and 5,743,586.
It has been found that the use of an expansible, self-curing foam to fill a cavity formed between two panels of truck box lids or tonneau covers can result in the appearance of a “roll” or “wave” in the lid or cover. The aluminum tread plate from which truck box lids are formed is relatively thin and subject to deflection when the foam cures. The result is one or more raised areas, especially toward the middle of the truck box lid, where the foam has expanded to such an extent that the exposed top sheet of the lid deflects outwardly forming a roll or wave that detracts from the overall appearance of the truck box.